1. Field of the Invention
This invention relates, in general, to machine tools and, more specifically, to tooling aids for machine tools for indicating the degree of squareness of the head of the tool with respect to the work table.
2. Description of the Prior Art
A variety of machine tools are utilized to perform various machining operations on a work piece or part. These machines, such as drill presses or milling machines, typically include a head and a spindle which holds and rotates a tool bit. The spindle may be raised and lowered to engage the tool bit with the work piece in performing a particular machining operation. The work piece is, in turn, releasably secured to a work surface or table by a fastening device, such as a vise or a chuck.
In order to insure a precision machining operation with accurate dimensions, it is necessary that the tool and thereby the head be properly aligned with the work table, i.e., that is, square or perpendicular thereto. This is especially critical in the initial set-up of a work piece or where the head is returned to a perpendicular position with respect to the work table after machining a prescribed angle.
Various types of indicating devices are known in the machining industry to measure the degree of squareness between the head of a machine tool and the work table. The most popular of these is the dial indicator which comprises a gauge that is attached to the spindle of the machine tool. A deflectable arm depends from the gauge to engage the surface of the work table. If the head is not square or perpendicular to the work table, the arm will deflect as the head is rotated about the work table, which deflection will be indicated by a deflection of a movable needle in the gauge to show the degree or amount that the head is out of square with respect to the work table.
Although dial indicators operate effectively to show the amount of deflection of the arm, the application of such dial indicators on vertical drill presses and milling machines poses several practical problems. For one, the work tables of small sized drill presses or verticle milling machine are approximately 9.times.12 inches, which, due to the relatively small size, limits the accurate measurement of the degree of squareness of the head since it is generally known that the larger the area measured, the more accurate the measurement will be. For another, conventional work tables are formed with parallel grooves for use with the various chucks and vises utilized to secure the work piece in position on the table. Such grooves interfere with the indicating arm as it is rotated about the work table and thereby reduce the reliability of the indicating measurement. In addition, crevices or holes are commonly formed in the surface of the work table over the period of time which further contributes to misleading measurements.
Thus, it would be desirable to provide a tooling aid for a machine tool which enables more accurate measurements of the degree of squareness between the head of the machine tool and the work table than previously possible utilizing prior art devices. It would also be desirable to provide a tooling aid suitable for providing an indication of the degree of squareness of the head of a machine tool with respect to the table which is easily applicable to conventional machine tools. Finally, it would be desirable to provide a tooling aid which increases the accuracy of standard dial indicators commonly used to measure the degree of squareness between the head of the machine tool and the surface of the work table.